The invention relates to drive means for a wire bonding apparatus to provide large bonding-plane regions to connect bonding loci via wire bridges, e.g. in connecting component-mounts or the like to the bonding islands of semiconductor chips by means of thermocompression- or thermosonic welding, at the wire ends.
With known apparatuses for wire bonding, the necessary z-direction movement is executed by the entire bonding head, including the generator system and the bonding implement attached thereto, and influenced by vertical guide means. In the present specification, the letters "x", "y" and "z" are used in the same sense as in U.S. Pat. No. 4,445,633, to designate a set of three orthogonal axes, "x" and "y" being in the plane of the workpiece and "z" being at right angles thereto (i.e., vertical). To increase operating speed, in other wire bonding apparatuses the generator system with the bonding element is swingably mounted in the bonding unit, namely in the form of a swingable link (German Democratic Republic Pat. No. 138,121); and the z-direction movement of the bonding implement is executed via a tilting movement of the generator system.
With the first of these solutions, the moving mass is very high, with the entire bonding head being moved, consequently, the bonding head tends to vibrate, thereby severely limiting the reliability of the bond, as well as the operating speed.
In the cases where the bonding implement is swingably mounted in the bonding unit, high operating speed can be achieved due to the lower mass. For reliable bonding, the bonding implement must always approach the bonding plane perpendicularly.ccordingly, the bonding implement must be in a single plane. As a result, the allowable variability in the bonding plane is sharply limited, or else when the bonding plane is changed the lever system must be repositioned. In the automatic high speed wire bonder "Model 1482" of the firm Kulicke and Soffa (USA), for example, the maximum tolerable bonding plane variation is only 0.75 mm. his limits the range of applicability of the apparatus to a few types of components.